1. Field of the Invention
The invention relates to a cam driven mechanism in which the rotating torque applied to a roller gear cam is converted to the oscillating rotational movement of a turret and an output shaft by means of a cam follower.
2. Description of the Related Art
The type of cam mechanism mentioned above, which has been proposed by Japanese utility model publication 7-52444 (Int.Cl.F16H 37/16), operates by means wherein the rotating movement input to a cam mechanism is converted into a oscillating rotational movement of an output shaft on the radial axis, and also a reciprocating movement of the output shaft in the axial direction. This type of mechanism is commonly applied to the tool changing mechanisms of metal processing machines with the purpose of obtaining a fast and precise tool change indexing action.
The aforesaid cam mechanism incorporates a roller gear cam fixedly attached to the input shaft, tapered ribs formed on the cam's periphery, and a cam channel formed on one of the cam's lateral surfaces. A roller cam follower, which is supported by a turret piece, rides between the aforesaid tapered ribs on the cam's periphery, and a swing arm rides in the aforesaid cam channel on the cam's lateral surface by means of a cam follower pin. An output shaft is installed through the turret's center by means of a sliding spline joint which fixedly connects the shaft to the turret in the radial direction, but allows free axial movement of the shaft through the turret piece in the axial direction. The end of the aforesaid swing arm is installed to the output shaft.
As a result of this configuration, the rotating movement of the input shaft is converted to an oscillating rotational movement of the output shaft by means of the aforesaid turret, and further converted to a reciprocating movement of the output shaft in the axial direction by means of the aforesaid swing arm.
A conventional cam mechanism of the type delineated above incorporates a turret whose cross section is shown in FIG. 11. As turret 1 is connected to output shaft 2 by means of a sliding spline joint, spline shaft 2a of output shaft 2 is of a square cross section which approximately corresponds to the square cross section of spline orifice 1a in turret 1. Peripheral surface 1b of turret 1 is of a round shape in radial cross section, and has installed to it six roller type cam followers 3. Cam followers 3, which ride in the area defined between the aforesaid tapered ribs 4 on the periphery of the aforesaid roller gear cam, are disposed around the periphery of turret 1 at regular intervals with their rotational centerlines C radiating from the center of turret 1 and output shaft 2.
As a total of six cam followers 3 are disposed around the periphery of turret 1, their orientation in relation to rectangular spline orifice 1a results in varying amounts of material existing between each cam followers 3 and output shaft 2. In other words, the volume of material in turret 1 between cam followers 3 and output shaft 2 is greatest in the area at the center and opposite to the flat surfaces of spline orifice 1a, and smallest in the areas adjacent to the corners of spline orifice 1a. As all of the six cam followers 3 cannot be oriented directly opposite the planar surfaces of spline orifice 1a where the volume of material is greatest, some of the cam followers 3 must be positioned in a way which reduce the amount of material between the cam follower 3 and spline orifice 1a.
As a result of this configuration, turret 1 must be designed so as to provide adequate strength and rigidity around the cam followers 3 which are supported by the smallest volume of material in relation to the splined orifice 1a, and in doing so there is created a surplus of rigidity and strength in the area where the cam followers 3 are supported by the largest amount of material. The result is that the periphery of turret 1 is made to relatively large dimensions which, in turn, results in the problem of the entire cam mechanism being made to a larger size than is desirable.